SPATIAL VARIATIONS IN THE RATE OF SEA-LEVEL RISE CAUSED BY THE PRESENT-DAY MELTING OF GLACIERS AND ICE SHEETS

The redistribution of surface water mass associated with the melting o f glacial ice causes uplift near areas of mass depletion, depression o f the seafloors, and changes in the earth's gravitational field which perturb the ocean surface. As a result, local spatial variations exist in the rate of sea level rise. Tide gauges on continental coastlines measure a sea level rise 5% smaller than the global average. Tide gaug es in the hemisphere opposite a source of continental mass depletion m easure sea level rise 10 to 20% greater than the global average produc ed by that source while satellites make measurements 10% too low. Beca use most long duration tide gauges are in the northern hemisphere, if the sources of sea level rise are unbalanced between the two hemispher es, estimates of global sea level rise could be in error by 10 to 20%. Individual tide gauges could be more seriously unrepresentative if th ey are near regions of significant present-day mass depletion.